Throughout the history of wastewater treatment, the focus has been on improving pollutant removal primarily by biological processes. Biological processes rely on aerobic, anaerobic, and facultative microorganisms to transform the organic matter and other recognized pollutants to benign gasses and dissolved or suspended solids that can be safely dispersed into the ground or receiving waters. There are a number of biological technologies and processes that are available to meet pollutant elimination discharge limits, but all operate at the ambient temperature of the sewage influent presented for treatment.
The aerobic treatment of sewage, and other biological feed stocks, involves the metabolic breakdown of organic matter by microbes in the presence of free oxygen. This process takes place in a containment vessel, such as a tank or basin, hereinafter termed “lagoon”. The lagoon is supplied with exogenous oxygen by submerged forced-air “bubblers” or by surface aerators. A noxious by-product of the metabolic breakdown, or digestion, is ammonia. When nitrosomonas bacteria are added in the presence of oxygen, the ammonia is converted to nitrite, which is then further transformed by oxidation to nitrate. The nitrate is ultimately consumed by facultative bacteria and turned into the beneficial gases of carbon dioxide (CO2) and nitrogen (N2) when the exogenous oxygen is depleted and the state of the lagoon turns from aerobic to anoxic.
The microbial action can be speeded by introducing heat. A known principle of metabolism, the Q10 principle namely, states that, within normal biological limits, a 10° C. rise in temperature will double the biochemical rate of reaction. Heating sewage influent could lead to exponential increases in microbial growth rates in a lagoon used for the treatment of wastewater, particularly where seasonal temperatures can drop to 0° C., or below. Furthermore, this increase in temperature, in turn, could allow more wastewater to be treated in a given vessel volume. In municipal wastewater treatment, where the scale is large, this volume efficiency could have significant implications for operational costs, not to mention facility construction costs, and would reduce the facility footprint impacting land use. The problem, however, is the prohibitive cost of supplying the heat.